What is vitamin D deficiency?
Vitamin D is essential for strong bones, healthy muscles and a robust immune system. When your level falls too low, this is called vitamin D deficiency.1 A milder shortage is often called insufficiency.1
Vitamin D status is commonly assessed by measuring the level of 25-hydroxyvitamin D (25[OH]D) in the blood, which is the main form of vitamin D circulating in the body.1 Here’s a quick guide:
Vitamin D blood test ranges1
| Category | Vitamin D level (ng/mL) | What it means |
|---|---|---|
| Deficient | Less than 20 ng/mL | Too low; treatment is usually needed |
| Insufficient | 21 to 29 ng/mL | Borderline low; at risk of deficiency |
| Optimal | 30 ng/mL and above | Healthy range for most people |
What does “ng/mL” mean?
“ng/mL” stands for nanograms per millilitre, a standard unit used in blood tests. Some labs use nmol/L instead. To compare:
- 20 ng/mL = 50 nmol/L
- 30 ng/mL = 75 nmol/L